Distance measurement sensor with Analog Ref

[andrewf]

Hi Guys,
I am trying to find a sensor that will measure up to a distance of 70m (230 feet) that has a 4-20mA output for the measurement feedback. it is only for an indicative position so accuracy is not that essential.

The application is to measure a trolley that moves backwards and forwards along a track, the trolley has not got that large of a surface area so i was looking at laser measurement but will take any suggestions. The only thing close so far that i can find is a LT3 sensor from Banner Engineering that will do 50m.
Any help is appreciated

Andrew

 

[Honga]

How is the trolley controlled?

What are you using the indicative position for?

 

[Eric Nelson]

The DT500 from Sick seems to fit your requirements. I have no idea how much these cost.

http://www.sick.com/group/EN/home/p...ensors/Pages/distance_sensors_long_range.aspx



-Eric

 

[sfindley]

Here is another option...no idea the cost.

http://www.dimetixlaser.com/

 

[andrewf]

Thanks for the suggestions guys, i will chase up some prices and report back.

How is the trolley controlled?

What are you using the indicative position for?

Trolley is used to store conveyor belt, one end is attached to a wire rope on a controlled drum that keeps tension and the other end has resistance from the belt. As the belt retracts the wire rope pulls in the trolley. So the measurement gives them an idea of how far the belt can retract. There are hard wired limits on the track that are used for cut offs.

We have previously used proxs on the rope drum but that does not work very well, i suppose another method would be some type of wire rope measurement?

 

[Plastic]

Can you put a CELESCO RT8000 absolute rotary transducer on your existing cable payout drum? (RT8000 can go up to 200 revolutions)

 

[andrewf]

Can you put a CELESCO RT8000 absolute rotary transducer on your existing cable payout drum? (RT8000 can go up to 200 revolutions)

Unfortunately measuring drum rotation will not work, the rotation of the drum is not linear to the amount of cable payed out or in.

 

[bkottaras]

Check this one out.
Not exactly what you asked for but at least it looks pretty cool.
I'd call and ask available lengths and such.
It can go up to 125" but these guys do custom stuff.
http://www.beiied.com/

 

[andrewf]

Check this one out.
Not exactly what you asked for but at least it looks pretty cool.
I'd call and ask available lengths and such.
It can go up to 125" but these guys do custom stuff.
http://www.beiied.com/

If you are talking about the linear cable transducer then something like that may work, although just having a look around now and the largest one i could find did about 40m and it was fairly big.
I am definitely open to any alternate ideas.

 

[Plastic]

Unfortunately measuring drum rotation will not work, the rotation of the drum is not linear to the amount of cable payed out or in.

Yes. I agree. Drum Rotation is not linear to cable payout, as the diameter of cable payout will change. BUT the payout is repeatable, you could wrtie a look-up table, or create an algorithm to account for payout circumfrence differential.

Line-Of-Sight laser is ok until visual accuity is obstrubtced or impaired.

The cable payout is the "real-deal" /"reel-deal". You can get ABSOLUTE position from it.